Insect wing circulation: transient perfusion through a microfluidic dragonfly forewing model.

Insect wings are made of an acellular composite material that forms a thin membrane and a complex network of veins. Veins are tubes that not only serve to stabilize the wing membrane, but they are also filled with hemolymph (insect blood). Thus, veins supply the sensory organs located on the wing veins with water and nutrients and enable the removal of waste products. In addition, the composite material of the wing is permanently hydrated by the hemolymph and thus retains the necessary flexibility. Hemolymph flow through the microfluidic vein network is therefore crucial for the functionality of insect wings. However, how perfusion occurs throughout the vein network in relation to hemolymph circulation is poorly understood. To investigate the dynamics of transient perfusion in complex wing venation, we developed a microfluidic wing vein model of the forewing of the common green darner dragonfly, Anax junius, using polydimethylsiloxane. Transient perfusion was simulated by injecting dye into the model filled with clear water; inversely, clear water was injected into dye in a separate trial. Visualized perfusion patterns suggest that the perfused portion of the vein network logarithmically increased with respect to time, which could be explained by a theoretical model of a simplified wing vein network, and that time differences occurred between the arrival of a new substance and the complete removal of an old substance in veins. Our biomimetic wing vein device enables further investigation into the unique circulatory system and transport phenomena of the insect wing. Also, our microfluidics-based approach proves a potential use of microfluidics in entomology and related fields.